Abnormal mucociliary clearance (MCC) is a critical component of cystic fibrosis (CF) lung disease, especially in the presence of infection; however, the mechanisms responsible for the defect are not well understood. Until recently, evaluation of this question has been primarily limited to cell culture models which do not replicate the complex nature of the airway surface or include contributions of the airway glands. Existing animal models of CF either do not accurately replicate lung pathophysiology (CF mice) or are very difficult and expensive to maintain for longitudinal studies to evaluate disease progress (CF ferret and pig). These challenges have left the CF research field deficient of an accessible animal model that can be readily used to evaluate airway physiology or response to pulmonary infection. Recently, I helped characterize the first CF rat, developed at our institution, which recapitulates a number of features highly relevant to human disease, due in part to expression of airway glands. This is a feature distinct from murine CF models, and provides an animal well suited for longitudinal evaluation and experimental manipulations. I have also recently established a method to chronically infect CF rats with mucoid Pseudomonas aeruginosa. To complement this, I have also advanced Micro-Optical Coherence Tomography (OCT), a high-resolution reflectance imaging modality that can simultaneously and non-invasively evaluate airway hydration, ciliary beating and mucus transport and viscosity in situ. Using these tools, this proposal will investigate the following independent but complimentary aims: 1. Establish the mechanism underlying abnormal mucociliary clearance in the CF rat. 2. Determine the mechanisms underlying increased susceptibility to Pseudomonas aeruginosa lung infection in the CF rat. 3. Does correction of the CFTR defect ameliorate P. aeruginosa susceptibility. This proposal will determine the early events that lead to infection and progression in CF pulmonary disease and how this relates to the formation and expression of airway glands. The studies will provide new fundamental observations that will inform our understanding of the CF respiratory pathology and help identify robust therapeutic targets suitable for intervention. Combined with a unique training program focused on optical imaging, mucus rheology, and microbiome analysis, this training period will position me for an independent scientific career investigating disorders of mucociliary clearance using cutting edge techniques.